1. Field of the Invention
The present invention relates to a serial (e.g., ink jet) recording apparatus, a serial recording method, and a serial recording program product each of which relates to the art of feeding, with a feeding roller, a recording medium and recording, with a recording head, an image on the recording medium.
2. Discussion of Related Art
There has conventionally been known an ink jet recording apparatus as a sort of serial recording apparatus that applies an ink to a recording sheet and thereby records an image on the sheet. The ink jet recording apparatus is employed as an image recording apparatus in, e.g., a facsimile apparatus or a printer apparatus.
Usually, the ink jet recording apparatus includes a recording head which has a plurality of ink jet recording elements arranged in one or more arrays in a sheet feeding direction and is mounted on a carriage that is moved by a drive source such as an electric motor in an image recording direction perpendicular to the sheet feeding direction; and a feeding roller which is driven or rotated by a drive source such as a stepper motor so as to feed the recording sheet in the feeding direction and thereby convey each portion of the sheet to a prescribed recording position where the recording head records a portion of an image on the each portion of the sheet.
When the image is recorded on the recording sheet, first, the feeding roller feeds the sheet to the recording position where the recording head is provided and, then, the respective recording elements of the head output respective inks toward the sheet while the head is moved in the recording direction.
Thus, an area where a portion of an image is recorded by one-time movement of the recording head in the recording direction is defined by a length in the feeding direction of the array of recording elements of the head, and is very narrow. Therefore, when a large image is recorded on a recording sheet, the feeding of each portion of the sheet by the feeding roller and the recording of each portion of the image by the recording head (i.e., the moving of the head in the recording direction and the outputting of the inks from the head) alternately occur.
When the large image is recorded on the recording sheet, as described above, it is needed to make an amount of feeding of the recording sheet by the feeding roller in the feeding direction (hereinafter, referred to as the “roller-feed amount”), equal to a length in the feeding direction of an image portion recorded on the sheet by one-time movement of the recording head in the recording direction, i.e., a length in the feeding direction of an area where inks are applied by the recording elements of the head to the sheet (hereinafter, referred to as the “head-record length”).
However, the conventional ink jet recording apparatus suffers a problem that because of manufacturing errors of the array of recording elements of the recording head and manufacturing errors of the feeding roller, there occurs a difference between the roller-feed amount and the head-record length. Thus, an image-spaced portion, i.e., a white line, or an image-overlapped portion, i.e., a black line is produced when an image portion is recorded by one-time movement of the head in the recording direction and successively the next image portion is recorded by the next one-time movement of the head in the recording direction.
The above-indicated problem is explained by reference to FIGS. 9A, 9B, and 9C. In those figures, “A” indicates a head-record length and “B” indicates a roller-feed amount. FIG. 9A shows an inappropriate case where an image-spaced portion, i.e., a white line, “s”, occurs to an image; FIG. 9C shows another inappropriate case where an image-overlapped portion, i.e., a black line, “u”, occurs to an image; and FIG. 9B shows a normal case where no white or black line occurs.
The reason why the white line shown in FIG. 9A occurs is that the roller-feed amount B is greater than the head-record length A defined by the length in the feeding direction of the array of recording elements, and the reason why the black line shown in FIG. 9C occurs is that the roller-feed amount B is smaller than the head-record length A.